add method to remove oldestCrashlogs. add CrashlogsFileFilter with unitTest class.

app/src/main/java/foundation/e/drive/fileFilters/CrashlogsFileFilter.java

+package foundation.e.drive.fileFilters;
+
+public class CrashlogsFileFilter {
+}

app/src/main/java/foundation/e/drive/services/ObserverService.java

@@ -37,6 +37,7 @@ import java.util.ListIterator;
 import java.util.Map;
 
 import foundation.e.drive.database.DbHelper;
+import foundation.e.drive.fileFilters.CrashlogsFileFilter;
 import foundation.e.drive.fileFilters.FileFilterFactory;
 import foundation.e.drive.fileFilters.OnlyFileFilter;
 import foundation.e.drive.models.SyncedFolder;
@@ -151,12 +152,36 @@ public class ObserverService extends Service implements OnRemoteOperationListene
         Log.i(TAG, "begin()");
         this.isWorking = true;
         clearCachedFile();
+        deleteOldestCrashlogs();
         startScan(true);
     }
 
+    /**
+     * This method remove all the crash-logs file
+     * in external dir that are 10 days or more old.
+     */
+    private void deleteOldestCrashlogs(){
+        Log.i(TAG, "deleteOldestCrashLogs()");
+        File[] fileToRemove = getExternalFilesDir(ServiceExceptionHandler.CRASH_LOG_FOLDER)
+                .listFiles(new CrashlogsFileFilter());
+
+        int counter = 0;
+        for (File file : fileToRemove) {
+            try {
+                file.delete();
+                ++counter;
+            }catch (SecurityException e){
+                e.printStackTrace();
+            }
+        }
+        Log.d(TAG, counter+" old crashlogs file.s deleted");
+    }
+
+
     /**
      * Clear cached file unused:
      * remove each cached file which isn't in OperationManagerService.lockedSyncedFileState();
+     * @TODO rewrite this method!
      */
     private void clearCachedFile(){
         Log.i(TAG, "clearCachedFile()");

app/src/test/java/foundation/e/drive/Test/FileFilterTest/CrashlogFileFilterTest.java

+package foundation.e.drive.Test.FileFilterTest;
+
+public class CrashlogFileFilterTest {
+}